Practical experience has revealed leakage losses in combustion engines and piston compressors that can be attributed to an incomplete seal. These leakage losses are identified as blowby gas and contain a significant amount of oil. The common approach with combustion engines is therefore to pass the blowby gas accumulating in the valve chamber back into the intake of the combustion engine. A known means for both the loss of oil through blowby gas while also ensuring optimal combustion and minimal impact on the environment is to separate oil from the blowby gas and to pass the separated oil back into the oil circulation system.
With a generic shaft, in particular a camshaft, evacuation of the blowby gas is effected through the tubular shaft part, and an oil separator can also be integrated directly into the tubular shaft part. One factor that must be taken into account is that the oil in the vicinity of a camshaft is frequently present in a wide variety of droplet sizes. Aside from the finest oil droplets that are contained in the blowby gas and are separated, for example by swirl generators, it frequently occurs that large oil droplets or splashed oil is observed in the area around a camshaft. Large oil droplets or splashed oil of this type can form, for example whenever an oil bath or oil foam is present at the camshaft. What can even occur in the worst cases is that a stream of oil reaches the shaft and, in particular, the tubular shaft part including the intake port for conducting the blowby gas.
Since implementing a follow-on separation of oil entails high costs, it is advantageous if large oil droplets, splashed oil, and oil streams can be kept away from the at least one intake port of the tubular shaft part in a generic shaft. Notwithstanding the ventilation and means of evacuating the blowby gas, it is then possible to keep the loss of oil as well as contamination of the downstream devices to a minimum. If a preferred embodiment has a downstream oil separator provided, for example inside the tubular shaft part, this oil separator then only has to separate the fine oil droplets from the blowby gas, thereby enabling an overall very efficient and reliable removal of oil to be achieved.
A shaft comprising the above-described features has been disclosed in EP 1 880 085 where a preseparator is provided on the outer surface of the shaft to separate oil, and a swirl generator integrated in the tubular shaft part is provided as the final separator. The preseparator is funnel-shaped and radially covers a plurality of radial intake ports of the tubular shaft part. The effective function as a splash guard is imperfectly achieved, however, since obliquely injected oil droplets or streams cannot be blocked. The preseparator is also of relatively costly design and requires a significant amount of installation space.